A typical vane-type camshaft phaser generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is selectively supplied to one of the advance and retard chambers and vacated from the other of the advance and retard chambers in order to rotate the rotor within the stator and thereby change the phase relationship between an engine camshaft and an engine crankshaft. Camshaft phasers also commonly include an intermediate lock pin which selectively prevents relative rotation between the rotor and the stator at an angular position that is intermediate of a full advance and a full retard position. The intermediate lock pin is engaged and disengaged by venting oil from the intermediate lock pin and supplying pressurized oil to the intermediate lock pin respectively.
Some camshaft phasers utilize one or more oil control valves located in the internal combustion engine to control the flow of pressurized oil to and from the advance chambers, retard chambers, and lock pin. One example of such a camshaft phaser is shown in United States Patent Application Publication number 2010/0288215. In this arrangement, three separate supply signals need to be included in the camshaft bearing for communication to the camshaft phaser. More specifically, a first passage for the advance chambers, a second passage for the retard chambers, and a third passage for the lock pin are included in the camshaft bearing. Including three separate passages in the camshaft bearing undesirably increases the length of the camshaft bearing. Additionally, space may be limited in the internal combustion engine to package oil control valves therein which are needed to control oil to and from each of the three passages.
In order to eliminate the packaging concerns and increased camshaft bearing length issues associated with packaging the oil control valve in the internal combustion engine, some manufacturers have included the oil control valve coaxially within the camshaft phaser. While this arrangement works well for oil control valves that supply oil only to the advance and retard chambers, controlling a lock pin with the same valve provides disadvantages. One example of such a camshaft phaser is shown in United States Patent Application Publication number 2004/0055550. One disadvantage of including a single oil control valve coaxially within the camshaft phaser to control oil to the lock pin in addition to the advance and retard chambers is the increased camshaft phaser thickness that is needed in order to accommodate the passage supplying oil to and from the lock pin. A single oil control valve also prevents independent control of the lock pin function and the phasing function which may make engaging the intermediate lock pin with its lock pin seat difficult.
What is needed is an axially compact camshaft phaser with valving for controlling the phase relationship and for controlling the lock pin which does not require three separate supply passages in the camshaft bearing. What is also needed is such a camshaft phaser which allows for control of the oil used for changing the phase relationship independent of the oil used for controlling the lock pin.